What kind of teachers does Chapter 48 explicitly state should not be considered a Sadguru?

Chapter 48 of the Sai Satcharitra makes a clear distinction between a true Sadguru and other types of teachers. The text cautions that wise men do not consider those who simply study the Vedas, have knowledge of the six Shastras, or explain Vedanta to be Sadgurus. Similarly, those who practice breath control (Pranayama), wear heated marks (Taptamudra), or please audiences with eloquent talks about Brahman fall short of the definition. The chapter further explains that gurus who give disciples mantras from scriptures to chant, but without any certainty of when the results will be attained, are not Sadgurus. The core issue identified is a lack of personal, direct experience, which renders their vast verbal knowledge as "verbally hollow."